How di I hook up 2 wifi G wireless routers to extend my wifi range and to act as a "repeater"?

Question

I have a 3 story house and I don`t get wifi reception 2 floors down

Answer 1

why is it you are trying to extend your range? are you  trying to work from 2 different floors or 2 different houses?

Answer 2

2 separate wireless routers will create two separate wireless networks.

Also to use 2 routers you need two ADSL lines & to switch from 1 network to other you will need to disconnect from one network & join the other network.

In other words switching (moving from one floor to another) wont be smooth but involves a manual disconnect.

What you need is an actual compatible repeater or an access point.